The hunt for stowaway bugs

Microorganism entering European airports incognito in the luggage of ordinary travellers unaware that they are potential health hazards for the residents of the country they visit

Custom officers are not the only ones with a keen interest in luggage content. Scientists too want to know what travellers are bringing into European airports. “A few weeks ago we had fresh meat samples from Ethiopia and from Vietnam in the packages of some travellers,” Martin Wagner, a microbiologist at the University of Veterinary Medicine in Vienna, Austria, says.

His interest in other people’s luggage stems from his role as the head of a new EU funded research project, called PROMISE, designed to identify microbial stowaways brought into the EU through what he estimates as tens of tonnes of illegally imported food, which could harbour human or animal disease or new resistant bugs. “We are now testing them and looking for what kind of pathogens they have and what the antibiotic resistance pattern of these bugs are,” Wagner says. Airport and port customs just do spot checks, so it is inevitable that a great deal gets through.

The aim of this research is to sketch out the risks posed by such bugs and give some advice to public health authorities as to what’s coming in. It could be that scientists find new genes harboured by these bugs or discover unwanted mini-travellers hiding in baggage, such as the virus which causes foot-and-mouth disease. They will also test for harmful food-borne bacteria such as Salmonella, Listeria, Campylobacter, E. coli and Staphylococcus aureus. “The PROMISE project is important because it is trying to uncover the scale of this sort of movement of foods,” Sarah O’Brien, a professor of infection epidemiology and foodborne diseases at the University of Liverpool, UK, says.

The problem is some bugs only affect the person who eats the food, but others like Salmonella or E. coli 157 can spread to other people. O’Brien adds: “And you are not just necessarily talking about the bugs that people have heard off, like Salmonella or E. coli 157 or Campylobacter, but depending on the origin of [food] like bush meat you might also be talking about more serious things like transmissible spongiform encephalopathies, which can lead to CJD [Cruetzfeldt-Jacob or mad cow disease].”

Others believe that the project is important because it should help to reduce the risks posed by illegal food imports contaminated with food poisoning bacteria. The problem is that “the incoming bacteria can be different from ‘local’ bacteria and more capable of establishing infections in previously unexposed populations,” explains David McDowell, food microbiology expert at Ulster University, UK, adding: “also, illegally imported foods may come from countries with very different approaches in the use of antibiotics, which can mean that the incoming bacteria are more resistant to some antibiotics, making it harder to treat any foodborne infections they cause.”

The key to halting new outbreaks of disease is to know your enemy. Until now, we did not know which bugs were coming into a country, where they were coming from and what threat they pose to people’s own health. “Since people are moving globally and goods are moving globally,” Wagner concludes “we thought one gap could be transmission of food pathogens through travelers.”